Figure 2

Bayesian network for assessing a single database ‘hit’. Structure of a Bayesian network for evaluating a correspondence (M₁) between the profile of a crime stain and that of a sample from a suspect when the suspect is on a database along with n−1 other individuals whose DNA profiles do not correspond. The size of the population of potential offenders is N. Among the N individuals, n (with n<N) are on a database. The node H has three states: ‘the suspect is the source of the crime stain’ (H₁), ‘the second individual in the database is the source of the crime stain’ (H₂), and ‘the source of the crime stain is among the N−n(here, n=2) individuals outside the database’ ($H_{3\text{\_}N}$). The corresponding genetic feature occurs in the population with rate γ. The node X₂is binary and represents the proposition according to which the profile of individual 2 (in the database) does not correspond to the crime stain.